Rollable blind assemblies are well known. Typically, they comprise a rotatable winding core and a shade material, arranged to be wound about and unwound from said winding core.
A problem with these known blind assemblies is that the winding core may sag under influence of gravity. This sagging may cause the shade material to ripple and wrinkle as illustrated in FIG. 1.
From DE102010034614 it is known that a shade supporting profile, such as an awning arm or a front rail, may sag during use. This may cause the associated shade material to wrinkle. It is proposed to provide the shade supporting profile in unloaded condition with a predetermined curvature that is neutralized by the sagging of the profile in loaded condition. As a result, the shade supporting profile may have a substantially straight shape during use.
This known solution only works for shade supporting profiles that during use do not alter their orientation with regard to the loading direction. It will not work for a rotating winding core. The predetermined curvature would only neutralize the sagging in one specific orientation of the winding core, in which it is rotated such that the predetermined curvature lies exactly opposite the sagging direction of the winding core. When the winding core is subsequently rotated away from this specific orientation, the predetermined curvature will no longer exactly counterbalance the sagging effects and when rotated over more than 90 degrees, the predetermined curvature will start to aggravate the problem since the predetermined curvature extends in the same direction as the sagging direction. A further problem with this known solution is that the required predetermined curvature may vary per blind assembly, depending on for instance the dimensions and weight of the shade material and/or sagging characteristics of the winding core itself, etc. It is difficult enough to provide a winding core with a specific predetermined curvature. It is practically undoable to provide each winding core with a customized predetermined curvature.